1. Field of the Invention
The present invention relates generally to gas turbine blades having at least one chamber for circulation of a cooling fluid, which may be air obtained by deviation of a fraction of the flow delivered by a compressor associated with the turbine. The term "turbine blades" here includes the stationary vanes of a turbine nozzle as well as the moving blades of a rotor. More specifically, the invention involves a manufacturing process for such blades, blade sections (half-blades) used for practicing said process and the blades obtained through the process. It should be noted that the term "half blade" is not intended in the mathematical sense of the word "half", but rather designates two different elements, one including the concave face of the blade and the other its convex face.
2. Description of the Prior Art
French Pat. No. 1,276,994 describes a gas turbine blade in which are provided a cooling fluid circulation chamber running the length of the blade in proximity to its leading edge, a first rectilinear conduit situated between said chamber and the leading edge and parallel to the latter, and a connecting groove between the conduit and the chamber. The blade may further include a cooling fluid circulation chamber running the length of the blade in proximity to its trailing edge, a second rectilinear conduit situated between the chamber and the trailing edge, parallel to the latter and issuing into ports in the trailing edge, and a connecting groove between the conduit and the chamber.
In order to facilitate construction of the chambers, the blade is produced by brazing two complementarily shaped half-blades, one of which includes the convex face of the blade and the other its concave face. The sectional area of the chambers is divided between the two half-blades, which are brazed together at points close to the leading and trailing edges. However, it will be noted that the interface of the two half-blades contains irregularities such that the first rectilinear conduit and the corresponding groove lie entirely within the half-blade comprising convex face. The same is true for the area of the ports in the trailing edge.
The reasons for this arrangement of the interface are not given in the patent. However, they probably involve a precaution intended to ensure a precise fit between the two half-blades, with the irregularities of the interface acting as stops in order to avoid total or partial blocking of the ports and conduits by brazing.
However, this interface arrangement complicates inter alia the production of the facing surfaces of the half-blades, the machining of the first conduit (which must be drilled through along the entire length of the blade), and the machining of the ports in the trailing edge (which must be drilled from this edge).